In recent years, demand has been increased for laminated piezoelectric ceramic electronic components such as laminated piezoelectric actuators, which are able to acquire a large amount of displacement even at low voltages.
This type of piezoelectric ceramic electronic component is typically manufactured in such a way that ceramic green sheets to serve as piezoelectric ceramic layers and conductive layers to serve as internal electrodes are stacked alternately and subjected to co-firing. Furthermore, Ni which is relatively easily available at a low price is preferably used as an internal electrode material.
Also, lead-free piezoelectric ceramic compositions containing no Pb have been attracting attention for environmental care, etc. in recent years. In particular, KNbO3 based piezoelectric ceramic compositions with K located as a main constituent at the A site of a perovskite structure (general formula: ABO3) and Nb located as a main constituent at the B site thereof have been researched and developed actively, because the KnbO3 based piezoelectric ceramic compositions provide relatively high piezoelectric d constants (piezoelectric strain constants).
For example, Patent Document 1 discloses a piezoelectric ceramic composition which has a main constituent represented by the general formula {(1−x)(K1-a-bNaaLib)m(Nb1-c-dTacSbd)O3−xM2nM4O3}. In this formula, M2 represents at least one bivalent metal element selected from among Ca, Sr, and Ba, and M4 represents at least one tetravalent metal element selected from among Ti, Zr, and Sn, x, a, b, c, d, m, and n respectively fall within the ranges of 0.005≦x≦0.1, 0≦a≦0.9, 0≦b≦0.3, 0≦a+b≦0.9, 0≦c≦0.5, 0≦d≦0.1, 0.9≦m≦1.1, and 0.9≦n≦1.1, and at least one specific element selected from among In, Sc, Y, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Er, Yb, and Lu is contained in an amount of 0.1 to 10 mol in total with respect to 100 mol of the main constituent.
In Patent Document 1, the piezoelectric ceramic composition has compositional constituents as described above, and thus can be sintered stably in the atmosphere, thereby allowing for the achievement of piezoelectric ceramic electronic components which have a high relative dielectric constant and electromechanical coupling coefficient, and also have a high Curie point of Tc and a high piezoelectric d constant.
Patent Document 1: Japanese Patent No. 3945536